Apparatus for waste-water filtration

ABSTRACT

A multi-step press apparatus for sludge dewatering and waste water filtration comprising: a tank, an inflatable membrane, a level sensor, and a nozzle assembly.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/470,136, filed on May 11, 2012 and entitled “Apparatus forWaste-Water Filtration”, which is a continuation-in-part of U.S. patentapplication Ser. No. 12/405,898, filed on Mar. 17, 2009, now U.S. Pat.No. 8,197,686, entitled “Apparatus for Waste-Water Filtration,” whichclaims priority to Israeli Patent Application No. 190,571, filed on Apr.2, 2008, entitled “Apparatus for Waste-Water Filtration,” thedisclosures of which are incorporated by reference in their entireties.

BACKGROUND

Many innovative sludge dewatering technologies and products have beenimplemented in order to address issues related to better performance,higher throughput or cost efficiency. Due to concerns about globalwarming and energy costs, there has been an effort to employ systemswhich consume less electrical power, chemicals and washing water.

Any wastewater and sludge process requires dewatering in order tominimize transportation and disposal volumes. Usually sludge istransported after the clarification, inefficiently, due to having ahigh, 89-90% liquid content.

As an example, with a daily wastewater volume of 100 cubic meters perday at solids concentration of 1000 parts per million, and when theclarifier used is DAF (dissolved air filtration), then an approximatesludge yield is approximately 2000 kg, or approximately 2 cubic metersper day, which contains approximately 5% dry solids. After pressing, thevolume of this sludge that contains 30% Dry solids reaches approximately330 liters (disposal volume).

The three major methods of achieving this dryness are plate filterpress, belt press, and centrifugal decanter.

Belt press and centrifugal decanters have proven to be too large anduneconomical for the volume in the example above, besides having otherdrawbacks, such as high power consumption and being too mechanicallycomplex and therefore costly.

Filter presses are usually manually operated and, therefore, requireclose operator attention. These presses quickly become dirty,necessitating periodical filter media cleaning.

In U.S. Pat. No. 5,614,092 to Di Leo, there is disclosed a filter systemfor the separation of solids and liquids from industrial muds. Thefilter in the system includes a deformable membrane and a fluid pumpwhich varies the size of the volume of the membrane, thereby squeezingthe filter.

While alleviating many of the tasks related to dewatering muds, such assqueezing and filtering, the filter disclosed in this patent does notaddress the need to minimize the down time due to the need to remove andclean the filter between the filtering operations, and, furthermore,does nothing to eliminate the need for man-hour input required for thecleaning.

SUMMARY

It is therefore desireable to obviate the disadvantages of prior artsludge filter and to provide a sludge filtering device which is capableof continuous operation and minimal or no down time.

It is also desireable to provide a sludge filtering device which iscapable of high yield and would be easy to manufacture and operate.

In a first embodiment disclosed herein is a multi-stage press apparatusfor automatic, PLC (programmable logic controller) controlled, sludgedewatering and waste water filtration, comprising:

a substantially cylindrical tank for receiving a mixture of sludge orwaste water and coagulant, the cylindrical tank being designed toeffectively allow suspended solids to be separated and later dewatered,and being provided with a lower, openable port for discharge ofdewatered solids and having a substantially vertical cylindrical doublelayer mesh wired screen for discharge of cleared liquid;

a centralized inflatable membrane, positioned to press the solidsagainst the screen, whereby a stream of discharged, cleared liquid,passes through the screen and is discharged to a sewage drain or afurther tank, the screen being provided with perforations sized toenable the passage of clear liquid therethrough while retaining fine andcoagulated solids on the internal surface thereof;

a load sensor in contact with the cylindrical tank to determine thecombined weight of the apparatus and of solid and liquid internallyretained thereon and to control the sequence of operation, and thefilling and pressing duration as a function of the weight, whereby asolids cake of about 30 mm thickness of fine and coagulated solids isformed and retained on the internal surface of the fine screen layer,thereby improving the filtering and dewatering capacity of theapparatus, the apparatus further comprising a bottom opening with asecond pneumatic inflatable membrane to seal and to open the bottomopening and thereby enabling downward discharge of solids into a sludgecollecting bin;

a set of high pressure nozzles located on the external side of the meshscreen body, to efficiently wash the screen from outside to inside, thenozzles being operationally linked to a drive mechanism which moves thenozzle assembly up and down in response to a PLC command during thecleaning cycle; and

a PLC provided to manage all cycles of operation along with pneumaticand other electrical control items to activate solenoid valves, pumpsand load cells, and to provide for a continuous dewatering andfiltration operation.

In a preferred embodiment of the present invention there is provided apress apparatus as defined above, further comprising a first tankprovided with a sludge or waste water inlet pipe to supply sludge orwaste water comprising a mixture of solids and liquid to the first tank;a pumping device, and a means for adding a coagulant to the sludge orwaste water; and an outlet pipe leading to the cylindrical tank.

In another preferred embodiment of the present invention there isprovided a press apparatus wherein the inflatable membrane is formed ofrubber and is pneumatically inflatable.

In a further preferred embodiment of the present invention there isprovided a press apparatus further comprising a pneumatic vibrator toimprove the detachment of solids from the internal screen of the doublelayer mesh wired screen.

In a further preferred embodiment of the present invention there isprovided a press apparatus further comprising a liquid collecting sumppan, which is pneumatically displaceable upon the washing cycle, theliquid collecting sump pan being located below the press bottom tocollect the washing liquid into the sewage system or back to theprocessing tank.

In yet a further preferred embodiment of the present invention there isprovided a press apparatus wherein the screen is coated with a non-stickmaterial.

In another preferred embodiment of the present invention there isprovided a press apparatus wherein the load sensor is also used fordetermining the rate of weight loss of the combined weight.

In another preferred embodiment of the present invention there isprovided a press apparatus wherein the coagulants are selected from thegroup consisting of alum, ferric chloride, ferric sulfate, ferroussulfate, titanium dioxide, lime, polyacrylates, cationic polyamines,cationic resin amines, cationic polyacrylamides and anionicpolyacrylamides.

In another preferred embodiment of the present invention there isprovided a press apparatus wherein the set of nozzles is disposedgenerally surrounding the external side of the screen.

In a most preferred embodiment of the present invention there isprovided a press apparatus wherein the set of nozzles contains about 10to about 30 nozzles.

In a most preferred embodiment of the present invention there isprovided press apparatus wherein each of the nozzles ejects a jet ofliquid.

In a most preferred embodiment of the present invention there isprovided press apparatus wherein each of the nozzles ejects a jet ofair.

In another embodiment disclosed herein is a multi-step press apparatusfor automatic sludge dewatering and waste water filtration, comprising:a substantially cylindrical tank for receiving a mixture of sludge orwaste water and coagulant, said cylindrical tank being designed toeffectively allow suspended solids to be separated and later dewatered,and being provided with a lower, openable port for discharge ofdewatered solids and having a substantially vertical cylindrical filterscreen for discharge of cleared liquid; a centralized inflatablemembrane, positioned to press said solids against said screen, whereby astream of discharged, cleared liquid, passes through the screen and isdischarged to a sewage drain or a further tank, said screen beingprovided with perforations sized to enable the passage of clear liquidthere through while retaining fine and coagulated solids on the internalsurface thereof; a level sensor to detect when said tank has receivedsufficient sludge or waste water as to render the tank substantiallyfull and to control the sequence of operation, and the a filling andpressing duration as a function of said level, whereby a solids cake ofabout 30 mm thickness of fine and coagulated solids is formed andretained on the internal surface of the fine screen layer, therebyimproving the filtering and dewatering capacity of the apparatus, saidapparatus further comprising: a bottom opening with a second pneumaticinflatable membrane to seal and to open said bottom opening and therebyenabling downward discharge of solids into a sludge collecting bin; anozzle assembly including a set of high pressure nozzles located on theexternal side of the double layer mesh wire screen body, to efficientlywash the screen from outside to inside, said nozzles being operationallylinked to a drive mechanism which moves said nozzle assembly up and downin response to a controller command during the a cleaning cycle; and acontroller provided to manage all cycles of operation along withpneumatic and other electrical control items to including activatingsolenoid valves, pumps and load cells, to provide for a continuousdewatering and filtration operation.

Yet further embodiments will be described hereinafter.

The invention will now be described in connection with certain preferredembodiments with reference to the following illustrative figures so thatit may be more fully understood.

With specific reference now to the figures in detail, it is stressedthat the particulars shown are by way of example and for purposes ofillustrative discussion of the preferred embodiments of the presentinvention only, and are presented in the cause of providing what isbelieved to be the most useful and readily understood description of theprinciples and conceptual aspects of the invention. In this regard, noattempt is made to show structural details of the invention in moredetail than is necessary for a fundamental understanding of theinvention, the description taken with the drawings making apparent tothose skilled in the art how the several forms of the invention may beembodied in practice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general diagrammatic view of a preferred embodiment of theapparatus according to the invention;

FIGS. 2 a and 2 b are sectional views of the apparatus with the internalparts, at filling cycle;

FIG. 3 is a sectional view of the apparatus with the internal parts, atpressing cycle;

FIG. 4 is a sectional view of the apparatus with the internal parts, atunloading cycle;

FIG. 5 is a sectional view of the apparatus with the internal parts, atcleaning cycle; and

FIG. 6 is a diagramatic description of sludge and wastewater modes.

FIG. 7 a is a side view of a scraper.

FIG. 7 b is a perspective view of a scraper

FIG. 7 c is a top view of a scraper.

FIG. 8 a is a side view of a filter apparatus showing the location of ascraper cylinder.

FIG. 8 b is a section of FIG. 8 a showing a scraper plate.

FIG. 9 is an enlarged perspective view of a scraper.

FIG. 10 is a side perspective view showing a scraper mechanismattachment.

FIG. 11 is a side perspective view showing the scraper and actuator.

FIG. 12 is a view showing a level sensor.

FIG. 13-15 are different views of a screen.

FIG. 16 is a view of a bottom sealing membrane.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows one embodiment of a multi-stage apparatus 10 for continuoussludge dewatering and waste water treatment.

A first tank 11 is provided with a wastewater inlet pipe 12 arranged tosupply thereinto sludge or waste water containing suspended solids. Thefirst tank 12 is further provided with a coagulant inlet 34 to mixcoagulant into the wastewater 12 introduced therein. The coagulant isactivated while mixed in a tank 33 by a mixer, or circulation pump 35.Addition of the coagulant enhances the efficiency of operation of thesubsequent stages, and further chemical additions may provided throughan inlet 15, wherein activation thereof is performed by the static mixer24, and activation duration is provided in a pipe flocculator 16.

Coagulant 34 may suitably be selected from the group consisting of alum,ferric chloride, ferric sulfate, ferrous sulfate, TiO₂, lime, andpolyacrylate flocculent 15 such as cationic PAM (polyacrylamide),cationic polyamine, cationic resin amine and anionic PAM(polyacrylamide).

First tank 12 is provided with a pump 14 for feeding the sludge orwastewater according a command from a PLC 21. PLC 21 receives signalsfrom a level detector 13 positioned on top of first tank 11. PLC 21controls dosage of chemicals 34 and 15, as long as pump 14 operates.

As used herein, level detectors and level sensors can include one ormore sensors useful for determining the level of a liquid, a solidand/or combinations thereof. Such sensors can include single pointsensors (e.g. level switches) and continuous transmitters of a signalrelated to the level and combination level sensors. Such sensors can bebased on any suitable technology, such as conductivity, magnetic,resistance, ultrasonic, capacitance, radar, laser, radiation,mechanical, pressure, differential pressure, weight, radio frequency,optical properties, as well as other technologies and combinations oftechnologies. Such sensors can be positioned, as appropriate for thedevice, in the cylinder or in some other portion of the filtrationdevice, including the top or the bottom, or for some embodiments and forsome technologies, nearby to the filtration device. In some embodiments,more than one level sensor can be used.

During a filling step, multistage press 10 is fed solids and liquidmixture via a conduit 17. Prior to the filling step, the weight of theempty press is detected by a load cell 20, and is registered by PLC 21.

In various embodiments, different types of controllers can be used inplace of a PLC. As used herein, a controller can include one or moresingle loop controllers, PLCs, distributed controllers, etc. as well ascombinations of these devices.

Press 10 further contains a rubber membrane 39 with an air inlet 19, abottom sealing membrane 36, a double layer screen mesh 37, a cleaningmechanism 38, a vibrator 18, a liquid sump receptacle 22, a pneumaticrotating cylinder 25, and a pneumatic controller 26.

Filling step is initiated by a signal from level sensor 13, signalingthe PLC that a sufficient amount of sludge or wastewater is present intank 12. The end of the filling cycle is determined by counting time orby feedback from load cell 20, therefore allowing the filling time tovary between cycles, assuring the shortest possible filling, regardlessof other process parameters. A control algorithm in PLC 21 analyses thesignals from load cell 20 throughout the stages and dynamically adjuststhe cycle duration as a function of the weight of solids-liquid mixtureinside apparatus 10.

Following the filling cycle, there follows the pressing, unloading andsubsequent cycles which are be explained hereinafter.

At the end of the unloading cycle, the unloaded weight of the solids 32dumped into container 27, is registered by the PLC for logistic or otherpurposes.

Apparatus 10 is firmly mounted on a metal structure 23, above a solidscontainer 27. The liquid that is pressed from the sludge or wastewateris discharged onto a sump 22 and then from pipes 29 or 30, depending onthe state of a directional valve 28, to the sewage, or back to thesludge or to a wastewater storage tank.

Details of the operation cycle for one embodiment are furtherillustrated in the following drawings.

There is seen in FIGS. 2 a and 2 b, a sectional view of embodiments ofthe apparatus with the internal parts thereof, during a filling cycle. Aflocculated and coagulated mixture 42 of solids and liquid, orwastewater is entering via port 53 onto a cylindrical void found betweenthe internal fine mesh screen 41, preferably of 60-200 mesh, which issupported by an external cylindrical coarse mesh screen 31, preferably4-10 mesh, and assembled onto a cylindrical pipe housing 55, which isfurther attached by rods 49, screws, bolts and Bellville® springs, andspring washers 47 to a main supporting structure 23, and the flexiblerubber membrane 39, of 40-60 Shore hardness, made from natural rubber,EPDM, polyurethane, or other rubber types.

The clean liquid expressed from mixture 42 is percolated outwardlythrough a fine screen 41 and a coarse screen 31, and a flow 48 isdrained into sump pan 22, which can be moved aside by pneumatic cylinder25, and further via pipe 30 or 29 depending on the position of valve 28,while the flocculent solids are retained between fine mesh screen 41 andthe squeezing action of a flexible rubber membrane 39. Low pressure airmay be applied through port 19, at pressures of 0.5-16 bar, to theinside volume of rubber membrane 39, in order to accelerate the rate ofpercolation.

The solids-liquids mixture is prevented from a downward flow, by asecond rubber membrane 36 being pressurized from port 56 at a regulatedair pressure. Membrane 36 is made of the same material as membrane 39.

The net weight of the mixture as measured by load cell 20 varies withtime, and the load cell measures the net weight accumulation of solidsand liquid retained in the void between membrane 39 and screen 41. Atthe start of the filling cycle the net weight changes slowly since mostof the liquid 50 percolates over screen 41, however, when the screenbecomes partly clogged the rate of increase of the net weight rises,until the whole void is full, at which point the pressure in the voidrises also, at about 0.5-16 bar filling pressure, whereupon an auto airregulator stops supplying air to air diaphragm pump which pumps mixture42 through port 53, and no more mixture is fed thereinto. Thereupon loadcell 20 detects the occurrence, the PLC sends a command to stop thefilling and feeds of chemicals.

Other parts of a press which can be seen in these embodiments includethe following:

the vertical supporting beams 46, the load cell moment release shaft 44,and a pneumatic rod less cylinder 40 which moves a set of nozzles 38,which receive the cleaning medium through a flexible tube 52 and a port54. There is also seen a splash protector 51 which is made of metal orplastic;

a pipe 43, clamped by a bolt, which connects rubber membrane 36 toanother pipe 57 by a screwed connection 58, and, similarly, an upperbolt 59 which connects membrane 39, to the top plate 45 with internalair conduits leading from ports 19 and 56; and metal pipes 43 and 57which form air-tight connections with the membranes.

The scraper 70, shown in FIG. 2 b, can be a construction of metal rings(as shown in FIG. 9) with blades as seen in FIGS. 7 a and 7 b, welded tothe rings, those blades can assist in pushing down the dry sludge, and atighten mechanism to an upper pneumatic or hydraulic cylinder 71 (FIGS.10 and 11), when activated by the PLC, or other controller, whiledownloading the sludge, will promote the release and removing of thedewater sludge into a disposal container or sludge conveyor.

When the sludge retained 42, is reaching the top, it will touch theelectrode tip 75 (for example when using a multi-rod electrode levelswitch sensor), and an electrical circuit between the press body and thesludge will be closed and therefore a signal to the PLC or othercontroller will indicate that the cylindrical tank is full and pressingoperation can start. The general assembly of such a sensor can be seenin, for example, in FIG. 12 and athttp://www.globalw.com/support/wl200install.html.

Also in FIG. 2 b we can see the new designed bottom sealing membrane 36,this flat membrane push up the sealing plate 36 a while inflated againstthe bottom opening, supported by a sliding plate 36 b, and open side waywhen deflated by cylinder 36 c, a semi open bottom sealing mem assemblycan be seen in FIG. 16.

In one embodiment, the screen can be a round shape cylindrical, openboth sides, its duty is to hold the cake and allow water to percolateoutside, see FIGS. 13-15.

There is seen in FIG. 3, a sectional view of the press with the internalparts thereof, during a pressing cycle.

The pressing cycle follows the filling cycle wherein the lower bottomremains closed by membrane 36, which receives air pressure of 4-16 barsfrom port 56, while membrane 39 receives compressed air via port 19,thereby inflating the membrane and pressing the solids-liquid mixtureagainst screen 41, causing a formation of cake 60, having a thickness of5-50 mm, according to the pre-programmed parameters in the PLC, whichmonitors cake thickness via input from load cell 20.

Excess liquid 48 is drained off, through the lower pan 22, via pipes 29,or 30, controlled by manual or automatic valve 28.

The end of a cycle is determined either by weight measurement via loadcell 20, by reaching the pre-programmed weight value, or by time count,whichever comes first.

Another option for stopping the pressing cycle is by the measurement ofweight loss rate, in order to determine when the rate of loss is belowthe end value of the pressing cycle.

There is seen in FIG. 4 a sectional view of the apparatus with theinternal parts thereof, during an unloading cycle. The bottom openingmembrane 36 is opened, by relieving the air, thereby creating a passageto void 61.

Upper membrane 39 is contracted as a result of air being released, and,at this point, a vibrator 18 may be activated to apply verticalvibration that causes a dewatered solids layer 60 to detach from ascreen 41 surface, with the vibrator being activated continuously orperiodically according to a program stored in the PLC. Air may be blownfrom a ring 38 of nozzles surrounding external screen 31. Air isdelivered to the nozzles via port 54. Ring 38 is capable of being movedup and down by the action of an air piston 40. This vertical movementenables a thorough, air backwashing of the whole surface of screen 41,thereby assuring a successful detachment of solids layer 60.

Dry solid layer 60 collapses and accumulates in a solids container 27.

There is seen in FIG. 5 a sectional view of the press with the internalparts thereof, during a screen cleaning cycle.

Following unloading of the press apparatus, and before starting a newset of cycles, a screen 41 surface must be free and clean of dirt.Screen 41 may be permanently coated with a layer of a non-stick materialsuch as Teflon®, or sprayed with a material of similar properties, toprevent dirt adhesion. Some solids will always be retained on the screensurface, however, and this cycle serves to remove the remaining dirtwith minimum amount of backwashing liquids such as water.

A liquid sump or a receiver 22, is swung into position by a pneumaticactuator 25, whereupon the main washing function is being performed byring 38 of nozzles, preferably composed of about 10-30 nozzles. Thenozzles generate a planar stream of liquid or air, the pressure thereofpreferably being between 3 to 20 bars, and total backwashing flow ratepreferably being between 5 to 20 liters per minute. The pressurizedliquid is delivered from a port 54 to the movable ring of nozzles by aflexible pipe 52.

The nozzles circumferentially surround screen 31 and generateoverlapping spray patterns. The clearance between exhaust tips of thenozzles to the external surface of screen 41 is preferably 10-50 mm.

The ring of nozzles is moved along the vertical axis upon a command fromthe PLC to a rodless pneumatic cylinder 40, whereupon the dirt trappedinside the holes in screen 37 is dislodged by liquid jets from nozzles38, and can be seen contained in stream 62 which flows downward,directed by a receiver 22 and ducted exterior to the press apparatus viapipe 29 or 30 as controlled by valve 28.

There is seen in FIG. 6, is a diagrammatic description of sludge andwastewater modes.

It will be evident to those skilled in the art that the invention is notlimited to the details of the foregoing illustrated embodiments and thatthe present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

Further having now described the invention in accordance with therequirements of the patent statutes, those skilled in this art willunderstand how to make changes and modifications to the presentinvention to meet their specific requirements or conditions. Suchchanges and modifications may be made without departing from the scopeand spirit of the invention as disclosed herein.

The foregoing Detailed Description of exemplary and preferredembodiments is presented for purposes of illustration and disclosure inaccordance with the requirements of the law. It is not intended to beexhaustive nor to limit the invention to the precise form(s) described,but only to enable others skilled in the art to understand how theinvention may be suited for a particular use or implementation. Thepossibility of modifications and variations will be apparent topractitioners skilled in the art. No limitation is intended by thedescription of exemplary embodiments which may have included tolerances,feature dimensions, specific operating conditions, engineeringspecifications, or the like, and which may vary between implementationsor with changes to the state of the art, and no limitation should beimplied therefrom. Applicant has made this disclosure with respect tothe current state of the art, but also contemplates advancements andthat adaptations in the future may take into consideration of thoseadvancements, namely in accordance with the then current state of theart. It is intended that the scope of the invention be defined by theClaims as written and equivalents as applicable. Reference to a claimelement in the singular is not intended to mean “one and only one”unless explicitly so stated. Moreover, no element, component, nor methodor process step in this disclosure is intended to be dedicated to thepublic regardless of whether the element, component, or step isexplicitly recited in the Claims. No claim element herein is to beconstrued under the provisions of 35 U.S.C. Sec. 112, sixth paragraph,unless the element is expressly recited using the phrase “means for . .. ” and no method or process step herein is to be construed under thoseprovisions unless the step, or steps, are expressly recited using thephrase “comprising the step(s) of . . . .”

Concepts

-   1. A multi-step press apparatus for automatic, PLC controlled,    sludge dewatering and waste water filtration, comprising:

a substantially cylindrical tank for receiving a mixture of sludge orwaste water and coagulant, said cylindrical tank being designed toeffectively allow suspended solids to be separated and later dewatered,and being provided with a lower, openable port for discharge ofdewatered solids and having a substantially vertical cylindrical doublelayer mesh wired screen for discharge of cleared liquid;

a centralized inflatable membrane, positioned to press said solidsagainst said screen, whereby a stream of discharged, cleared liquid,passes through the screen and is discharged to a sewage drain or afurther tank, said screen being provided with perforations sized toenable the passage of clear liquid therethrough while retaining fine andcoagulated solids on the internal surface thereof;

a load sensor in contact with the cylindrical tank to determine thecombined weight of the apparatus and of solid and liquid internallyretained thereon and to control the sequence of operation, and thefilling and pressing duration as a function of said weight,

whereby a solids cake of about 30 mm thickness of fine and coagulatedsolids is formed and retained on the internal surface of the fine screenlayer, thereby improving the filtering and dewatering capacity of theapparatus, said apparatus further comprising:

a bottom opening with a second pneumatic inflatable membrane to seal andto open said bottom opening and thereby enabling downward discharge ofsolids into a sludge collecting bin;

a set of high pressure nozzles located on the external side of the meshscreen body, to efficiently wash the screen from outside to inside, saidnozzles being operationally linked to a drive mechanism which moves saidnozzle assembly up and down in response to a PLC command during thecleaning cycle; and

a PLC provided to manage all cycles of operation along with pneumaticand other electrical control items to activate solenoid valves, pumpsand load cells, to provide for a continuous dewatering and filtrationoperation.

-   2. A press apparatus according to concept 1 further comprising a    first tank provided with a sludge or waste water inlet pipe to    supply sludge or waste water comprising a mixture of solids and    liquid to said first tank, a pumping device, and a means for adding    a coagulant to the sludge or waste water and an outlet pipe leading    to said cylindrical tank.-   3. A press apparatus according to concept 1, wherein said inflatable    membrane is formed of rubber and is pneumatically inflatable.-   4. A press apparatus according to concept 1, wherein said inflatable    membrane is formed of rubber and is hydraulically pressurized.-   5. A press apparatus according to concept 1 further comprising a    pneumatic vibrator to improve the detachment of solids from the    internal screen of said double layer mesh wired screen.-   6. A press apparatus according to concept 1 further comprising a    liquid collecting sump pan, which is pneumatically displaceable,    upon the washing cycle, said liquid collecting sump pan being    located below the press bottom to collect the washing liquid into    the sewage system or back to the processing tank.-   7. A press apparatus according to concept 1, wherein said screen is    coated with a non-stick material.-   8. A press apparatus according to concept 1, wherein said load    sensor is used for determining the rate of weight loss of said    combined weight.-   9. A press apparatus according to concept 1, wherein said coagulants    are selected from the group consisting of alum, ferric chloride,    ferric sulfate, ferrous sulfate, titanium dioxide, lime,    polyacrylates, cationic polyamines, cationic resin amines, cationic    polyacrylamides and anionic polyacrylamides.-   10. A press apparatus according to concept 1, wherein said set of    nozzles is disposed generally surrounding said external side of said    screen.-   11. A press apparatus according to concept 10, wherein said set of    nozzles contains about 10 to about 30 nozzles.-   12. A press apparatus according to concept 1, wherein each of said    nozzles ejects a jet of liquid.-   13. A press apparatus according to concept 1, wherein each of said    nozzles ejects a jet of air.

We claim:
 1. A multi-step press apparatus for automatic sludgedewatering and waste water filtration, comprising: a substantiallycylindrical tank for receiving a mixture of sludge or waste water andcoagulant, wherein said cylindrical tank being designed to effectivelyallow suspended solids to be separated and later dewatered, and beingprovided with a lower, openable port for discharge of dewatered solidsand having a substantially vertical cylindrical filter screen fordischarge of cleared liquid; a centralized inflatable membrane,positioned to press said solids against said screen, whereby a stream ofdischarged, cleared liquid, passes through the screen and is dischargedto a sewage drain, said screen being provided with perforations sized toenable the passage of clear liquid there through while retaining fineand coagulated solids on the internal surface thereof; a level sensor todetect when said tank has received sufficient sludge or waste water asto render the tank substantially full and to control a sequence ofoperation, and a filling and pressing duration as a function of saidlevel, whereby a solids cake of about 30 mm thickness of fine andcoagulated solids is formed and retained on the internal surface of thecylindrical filter screen, thereby improving the filtering anddewatering capacity of the apparatus, said apparatus further comprising:a bottom opening with a second pneumatic inflatable membrane to seal andto open said bottom opening and thereby enabling downward discharge ofsolids into a sludge collecting bin; a nozzle assembly including a setof high pressure nozzles located on the external side of the screen, towash the screen from outside to inside, said nozzles being operationallylinked to a drive mechanism which moves said nozzle assembly up and downin response to a controller command during a cleaning cycle; and acontroller provided to manage all cycles of operation along withpneumatic and other electrical control items including activatingsolenoid valves, pumps and load cells, to provide for a continuousdewatering and filtration operation.
 2. The press apparatus of claim 1further comprising a pneumatic activated scraper to detach solids fromthe screen.
 3. The press apparatus of claim 1, wherein said level sensorgenerates a signal which can be used to determine a rate of filling. 4.The press apparatus of claim 1, wherein the level sensor is located ontop of the said substantially cylindrical tank.
 5. The press apparatusof claim 1, wherein the controller is a PLC.
 6. A multi-step pressapparatus for automatic sludge dewatering and waste water filtration,comprising: a substantially cylindrical tank for receiving a mixture ofsludge or waste water and coagulant, wherein said cylindrical tank beingdesigned to effectively allow suspended solids to be separated and laterdewatered, and being provided with a lower, openable port for dischargeof dewatered solids and having a substantially vertical cylindricalfilter screen for discharge of cleared liquid; a centralized inflatablemembrane, positioned to press said solids against said screen, whereby astream of discharged, cleared liquid, passes through the screen and isdischarged to a further tank, said screen being provided withperforations sized to enable the passage of clear liquid there throughwhile retaining fine and coagulated solids on the internal surfacethereof; a level sensor to detect when said tank has received sufficientsludge or waste water as to render the tank substantially full and tocontrol a sequence of operation, and a filling and pressing duration asa function of said level, whereby a solids cake of about 30 mm thicknessof fine and coagulated solids is formed and retained on the internalsurface of the cylindrical filter screen, thereby improving thefiltering and dewatering capacity of the apparatus, said apparatusfurther comprising: a bottom opening with a second pneumatic inflatablemembrane to seal and to open said bottom opening and thereby enablingdownward discharge of solids into a sludge collecting bin; a nozzleassembly including a set of high pressure nozzles located on theexternal side of the screen, to wash the screen from outside to inside,said nozzles being operationally linked to a drive mechanism which movessaid nozzle assembly up and down in response to a controller commandduring a cleaning cycle; and a controller provided to manage all cyclesof operation along with pneumatic and other electrical control itemsincluding activating solenoid valves, pumps and load cells, to providefor a continuous dewatering and filtration operation.
 7. The pressapparatus of claim 6 further comprising a pneumatic activated scraper todetach solids from the screen.
 8. The press apparatus of claim 6,wherein said level sensor generates a signal which can be used todetermine a rate of filling.
 9. The press apparatus of claim 6, whereinthe level sensor is located on top of the said substantially cylindricaltank.
 10. The press apparatus of claim 6, wherein the controller is aPLC.